1. Field of the Invention
The present invention relates to aqueous compositions containing an ester-modified polyisocyanate, an aqueous polyester resin containing hydroxy groups and optionally urethane groups, and a physically drying, aqueous polyurethane resin, and to coatings prepared from these aqueous compositions which have improved resistance to suntan lotion.
2. Description of the Prior Art
Aqueous polyurethane coating compositions may be used for coating a wide variety of substrates, both rigid and flexible. One use for these compositions is for coating interior parts on automobiles. The coating compositions are based on a water dispersible polyisocyanate, an aqueous polyester urethane polyol and a physically drying aqueous polyurethane resin. The resulting coatings have what is known as a "soft feel," i.e., a leather-like feel.
When they are applied to interior surfaces, such as instrument panels, airbag covers, arm rests or interior door panels, they provide a soft, more desirable feel to these substrates. One of the disadvantages of these coatings is that they do not possess good suntan lotion resistance, which is one of the requirements of automotive manufacturers. Suntan lotion can penetrate through these coatings and cause delamination of the coating from the substrate.
Accordingly, it is an object of the present invention to provide improved coating compositions, which have sufficiently improved resistance to suntan lotion to pass the requirements of automotive manufacturers.
This object can be achieved with the coating compositions according to the present invention that are described hereinafter. It has been found that by incorporating ester groups into the polyisocyanate component, the suntan resistance of the resulting coatings can be improved.
It is disclosed in copending application, U.S. Ser. No. 08/666,166, that blends of physically drying (fully reacted) polyurethanes can be added to blends of two-component aqueous polyurethane coating compositions (a mixture of a water dispersible polyisocyanate and an aqueous polyester urethane polyol) to provide long processing times as well as rapid drying at room temperature. These coatings are particularly useful as wood coatings, e.g., for furniture and parquet flooring. However, this application does not disclose that the resistance to suntan lotion could be improved by modifying the polyisocyanate component in accordance with the present invention.